This proposal is for funds to develop light microscopic neuroanatomical techniques which can be integrated into neurophysiological and ultrastructrual studies of central nervous system connections. The majority of proposed experiments are related to the development of horseradish peroxidase histochemistry as an anatomical tool. Recent work in this laboratory has shown that this enzyme is accumulated by neurones and transported to their dendrites, axons, and terminals. Studies are described which should make this method: 1) applicable to the analysis of efferent projections of all brain systems; and 2) useable at the electron microscopic level. In addition data will be collected on bidirectional neuroplasmic flow and the possible existence of transsynaptic transport.